DE10207536A1 - Device for mixing fuel and an oxidizing agent - Google Patents

Abstract

An apparatus and method for mixing fuel and an oxidizer for use in an autothermal reformer that provides hydrogen to a fuel cell is provided. The apparatus includes a mixing tank, a first inlet to the mixing tank for moving a gaseous fuel or oxidizer therethrough, a second inlet for moving a gaseous fuel or oxidizer therethrough, and an outlet from the tank adjacent to the autothermal reformer. The discharge ends of the inlets are spaced from each other and from the outlet which is provided in the vicinity of a POX reactor which burns the mixture of fuel and oxidant leaving the mixing tank. The first inlet consists of a plate with a plurality of tubes extending therefrom and through which the fuel or oxidant passes. The tubes extend into the mixing container and toward the outlet of the container so that the fuel does not come into contact with the oxidant until the gaseous fuel or oxidant is discharged from the ends of the tubes, causing the fuel to oxidize in is mixed into the gaseous state prior to being directed to the POX reactor.

Description

FIELD OF THE INVENTION

The present invention relates to fuel processors for the delivery of Hydrogen on fuel cells and especially the mixing of Fuel and an oxidizer for use in an automobile thermal reformers.

BACKGROUND OF THE INVENTION

A fuel cell is an electrochemical device for continuous use chemical conversion - one fuel and one Oxidizing agents - in electrical direct current. It consists of two elect rically conductive electrodes, which are formed by an ion-conducting electrolyte are separated, taking precautions for the continuous movement of Fuel, oxidant and reaction product in and out of the cell the cell are provided. Fuel cells are different from Batte that electricity is generated from chemical fuels, which are fed to them as needed, so that their operating life it is theoretically unlimited. Fuel is at the anode (negative Electrode) oxidized, whereby electrons are given to an external circuit be. The oxidant picks up electrons from the anode and is reduced at the cathode. Simultaneously with the transfer of Electrons complete an ion current in the electrolyte the scarf  tung. The fuels are in the range of hydrogen and carbon containing materials up to redox compounds, alkali metals and biochemical materials. Fuel cells based on water Substance and oxygen are important sources of primary energy Future. Cells of this type are currently in use as an ener Energy source for electric vehicles developed, the hydrogen from Me ethanol, gasoline, diesel fuel or the like is derived.

Fuel cells, such as PEM fuel cells, have been proposed for many applications that include, for example, electrical power plants to replace internal combustion engines. PEM fuel cells are well known in the art and include a "membrane electrode assembly" (also known as MEA) that includes a thin proton permeable solid polymer membrane electrolyte having an anode on one side and a cathode on the opposite side. The solid polymer electrolytes typically consist of ion exchange resins, such as, for example, perfluorinated sulfonic acid. The anode / cathode typically comprises finely divided catalytic particles (often carried on carbon particles) mixed with proton-conductive resin. The MEA is sandwiched between a pair of electrically conductive elements that ( 1 ) serve as current collectors for the anode and cathode and ( 2 ) include channels for distributing the gaseous reactants of the fuel cell over the surfaces of the respective anode and cathode. In PEM fuel cells, hydrogen is the anode reactant (ie fuel) and oxygen is the cathode reactant (ie oxidant).

In automotive applications, it is desirable to have one over carbon bound hydrogen-containing fuel (for example methane, Ben zin, methanol, etc.) to use. Such liquid fuels are especially as a source of hydrogen from the fuel cell is used due to its easy storage on board and the Existence and availability of a wide infrastructure of petrol stations advantageous and desirable that such liquids are suitable and be can deliver quem. These fuels need to be broken down to release their hydrogen content to supply the fuel cell. The splitting reaction is carried out in a so-called "primary reactor" achieved, which is the first in a series of reactors that fuel processor includes. Other reactors serve in the fuel processor to remove CO from the hydrogen from the primary reactor is produced. Such a known primary reactor for gasoline is at for example a two-stage chemical reactor, often referred to as an "au tothermal reformer (autothermal reformer) ". In an auto thermal reformers (ATR) become gasoline and water vapor (i.e. steam) mixed with air and successively through two reaction sections led, d. H. a first "partial oxidation section" (POX section) and a second steam reforming section (SR section). By doing POX section reacts to gasoline using an open flame menbrenners (open flameor) or a catalytic converter exothermic with a substoichiometric amount of air to carbon monoxide, hydrogen and lower hydrocarbons such as methane The hot POX reaction products together with the steam that with which gasoline is introduced get into an SR section, in which is the lower hydrocarbons and a share of coal monoxides react with the steam to produce a reformate gas that  basically includes hydrogen, carbon dioxide and carbon monoxide. The SR reaction is endothermic but either receives its required heat of the heat generated in and in the exothermic POX section Direction of the SR section through the drain of the POX section out, or from other parts of the fuel cell system (at for example from a burner). Such an autothermal reformer is in International Patent Publication No. WO 98/08771 ben, which was published on March 5th, 1998.

Downstream of the ATR, the carbon monoxide contained in the SR effluent is removed or at least reduced to very low concentrations (ie less than about 20 ppm) that are not toxic to the anode catalyst in the fuel cell. For this purpose, fuel processors are known which clean the SR outflow of CO by first subjecting it to a so-called "water-gas shift" reaction (ie CO + H ₂ O → CO ₂ + H ₂ ) and then with oxygen (ie as air) in a so-called "reaction with selective / preferred oxidation" (ie CO + ½ O ₂ → CO ₂ ). The H ₂ -rich reformate cleaned from CO is then delivered to the fuel cell.

For effective operation of an ATR, it is very beneficial and he wishes if the gaseous fuel and the gaseous oxidati Onsmittel completely mixed before entering the POX section become. It is also particularly important that the mixture is a result of the Presence of oxidizing agent in the warmed environment mig of the POX does not start to burn prematurely. The present inven is to improve the mixing of fuel and oxidati onsmittel, which are supplied to a POX reactor, so a  Prevent premature burning or ignition of the mixture before this enters the POX reactor, and thereby the formation of coal remove particulate matter (i.e., soot) upstream of the POX.

It is an object of the present invention to provide a POX reactor see that has a mixing container at its inlet to burn Mix substance and oxidant by either fuel or oxidizing agent is introduced into the container at a first location and then the other from fuel or oxidant a second place is introduced, which is sufficiently downstream of the First place is arranged so that the mixture in the container is not recirculated, but rather directly unburned to the exit of the Container arrives. The fuel (or the oxidizing agent) leaves the Intake from a variety of closely spaced tubes that fit well terstromig to where the oxidant (or fuel) in the Mixing container is inserted, and in the direction of the POX reactor extend, reducing the amount of time during which the gas shaped fuel exposed to the oxidant in the mixing container is before the mixture enters the POX reactor, causing a premature Total burning of the fuel and consequently soot formation Chen is prevented.

SUMMARY OF THE INVENTION

An apparatus is described for fuel and an oxidation to mix for delivery to an ATR, the hydrogen for a Provides fuel cell. The device also includes a mixing container a first inlet for moving a gaseous fuel (or  Oxidant) through this and a second inlet for movement of gaseous oxidant (or fuel) through it, whereby the inlets from each other in the direction of flow through the container are spaced apart, and with an outlet that is from the inlets spaced and adjacent to a POX reactor which is the Mixture of fuel and oxidant that make up the mixing tank leaves, partially burned. The first inlet includes a plate with a variety of pipes extending from this and through wel the fuel and the oxidizing agent. The pipes extend itself in the mixing container, so fuel (or oxidizing agent) un downstream of the second inlet and near the outlet of the Be discharge, so that the fuel is not in contact with the oxidant comes until the gaseous fuel (or that Oxidant) emerges from the pipes, causing the fuel the oxidant in the gaseous state just before the transition into the POX reactor (e.g. into the catalyst reaction bed of a catalytic POX reactor) is mixed.

A method is also described to make fuel and an oxidati onsmittel in a container for delivery to a POX reactor to mi that includes gaseous fuel and gaseous oxide be mixed in the container in that fuel or oxidant passed through a first inlet of the container becomes; Oxidizer or fuel through a second inlet of the Container is guided, the inlets from each other and from one Outlet, which is arranged in the vicinity of a POX reactor, spaced are the mixture of fuel and oxidant that the Mixing container leaves, partially burned; with the first inlet off  a plate with a multitude of tubes consisting of this extend and through which the fuel or oxidant to be led; and with the pipes in the mixing tank nearby extend the outlet of the container and their gas downstream of the Discharge the discharge points of the second inlet so that the fuel as long as it does not come into contact with the oxidizing agent until the gas shaped fuel or the oxidant escapes from the pipes, whereby the fuel with the oxidant in the gaseous State just before the fuel and oxidant mixture passes through the outlet in the POX reactor, is mixed.

DRAWING SUMMARY

Fig. 1 is a front view of the mixing container for mixing gaseous fuel and gaseous oxidizing agent according to the present invention;

Fig. 2 is a top view of Fig. 1;

Figure 3 is a side sectional view of Figure 1 along lines 3-3;

Fig. 4 is a sectional view taken along lines 4-4 of Fig. 1;

Fig. 5 is a partially sectioned view taken along lines 5-5 of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be detailed in view of the following Description with reference to the accompanying drawings bes understandable. In the drawings, the same parts are the same Reference numerals.

The present invention relates to a device for mixing Fuel and an oxidizer for use in an ATR which Delivers hydrogen to a fuel cell. The mixture of fuel and oxidant is sent to a POX reactor in the ATR Combustion in it before it flows upstream of the POX Can ignite the reactor itself.

In an autothermal reformer, the air, fuel and Steam flows completely before entering the POX reactor section be mixed. Moreover, it is in terms of system efficiency desired to apply heat to these streams prior to mixing However, at high temperatures, which are typical for ATR's (about 500-600 ° C), the self-ignition delay times of Koh Hydrogen fuels relatively short (10-100 ms). If a self ignition occurs before the mixture enters the POX reactor, The gas phase reactions tend to deposit unwanted carbon stanchions (i.e., soot) that damage the POX reactor. This is especially difficult with catalytic POX reactors, because the soot Contaminated catalyst, which reduces its effectiveness and the Pressure loss increased by this. Therefore, it is necessary to burn Mix the substance and the oxidizing agent so that they are very short Have residence time in the mixer when the fuel cell, the  is located at full power, so the dwell time occurs when the fuel cell is at low power, still does not exceed the autoignition delay time. The residence time in the fuel processor increases with lower power, since the flow rates are reduced and the pressure is almost constant is.

The desired feature of the present invention is a distributed introduction of either the fuel or the oxidation medium downstream of one distribution plate to distribute the other of Provide fuel or oxidizing agent and thereby ensure that the gaseous fuel or oxidant is not in a Recirculation zone is introduced into the mixing container; what the ver increase in time and thereby lead to self-ignition would. The task is to mix the fuel and the oxidati onsmittel optimize, while at the same time the total residence time the mixture in the mixing container is reduced.

In Fig. 1, the mixing container 10 for mixing fuel and oxi dationsmittel for use in an ATR 12 downstream of the container ters 10 is shown. Fuel is introduced into the canister 20 via an inlet pipe 14 . The inlet pipe 14 has a series of openings 18 in its periphery that facilitate distribution of the gaseous fuel through a chamber 20 defined by an end cap 22 of the mixing container 10 . The gaseous fuel passes from the chamber 20 through a plurality of tubes 24 spaced by a first distribution plate 26 which defines the chamber 20 and exits through openings 30 at its distal ends which are substantially in the interior of the Mixing chamber 32 are arranged. The inlet pipe 14 has a pressure connection 15 connected to it. The mixing chamber 32 similarly has an associated pressure connection 34 .

In a preferred embodiment, steam and air are introduced into inlet 40 and enter tangentially via tube 46 into toroidal manifold 42 . The air is mixed with steam in a first annular chamber 41 of manifold 42 and passes through a porous (ie sintered) metal partition 48 positioned in the interior of manifold 42 and separating manifold 42 into first and second chambers 41 and 43 . The porous plate has an average pore size of about 100 microns and serves to aid mixing of the steam and air in chamber 41 and to distribute the gas flow uniformly into chamber 43 defined by the distribution plate 50 . As can be seen in FIGS. 4 and 5, the distribution plate 50 has a plurality of openings 52, whose diameter is greater than that of the tubes 24 and through which the tubes 24 pass. The mixture of steam and air enters the mixing chamber 32 via the annular gap 53 , which is defined by the outer diameter of the tubes 24 and the inner diameter of the opening 52 .

The object of the present invention is to facilitate the mixing of the gaseous fuel and the gaseous oxidizing agent (preferably air and steam) at a location 33 between the ends 30 of the tubes 24 and the outlet end 60 of the container and to prevent the mixture of oxidant and fuel are recirculated back to area 62 of mixing chamber 32 . In this regard, an imaginary line can be drawn at the bottom of the inlet pipe 46 , namely at reference number 47 . The upper portion 62 of the chamber 32 between the imaginary line 47 and the second distribution plate 50 is a high temperature recirculation zone in which turbulence and eddy currents prevail, which can prolong the residence time of gases trapped therein. The object of the present invention is to gasförmi gen fuel of the tubes 24 leaves the ends 30, to prevent from entering into the recirculation zone, this in the region between the tube ends 30 and 60 completely to mix the container outlet onsmittel with the Oxidati and to cause them all to move towards the catalyst bed 61 of the POX reactor 12 .

In order to achieve rapid mixing without having to move the oxidant and fuel mixture into the recirculation area, the fuel is fed into the air-steam flow through a large number (of the order of 100) of small diameter fuel tubes 24 ( see Figs. 4 and 5) distributed. A distribution of the fuel in the air-steam flow over a large number of insertion points ensures a uniform mixture near (ie within a short downstream distance from) the pipe ends. The smaller the distance between these insertion points, the less downstream distance is required to achieve a uniform mixture. In this regard, the downstream flow distance required for mixing is proportional to the distance between the injection points (ie pipe ends 30 ). A distance of about six times the distance of the fuel pipes 24 is desirable for mixing based on turbulent jet spread rates. In order to ensure a short dwell time, fuel-containing recirculation zones must be eliminated. This is achieved by introducing the fuel at the end 30 of small fuel tubes 24 and these tubes ending well downstream of the air and steam introduction plate 50 to introduce fuel into the recirculation zones associated with this plate to avoid. These recirculation zones extend to a downstream distance of approximately 2.5 times the space between the holes 52 in the plate 50 for the introduction of air and steam. The fuel pipes 24 should not be excessively long (just long enough to extend past the end of the recirculation zones from the insertion plate 50 ) so that the fuel is not heated by the hot air and steam flow through conduction through the fuel pipes 24 . Excessive heat of the fuel (up to about 600 ° C) could lead to undesired decomposition of the fuel.

Alternatively, the mixing can be accomplished by introducing ( 1 ) fuel and steam through tubes 24 (and air through plate 50 ), or ( 2 ) air through tubes 24 (and fuel and steam through plate 50 ) are introduced, or ( 3 ) air and steam through tubes 24 (and fuel through plate 50 ) are introduced.

The size of the tubes 24 can vary widely depending on the flow of the oxidant and the fuel, as well as the desired amount of mixing. It has been found advantageous that the tubes 24 have an outer diameter of approximately 0.0625 inches (approximately 0.15875 cm) with a wall thickness of 16 mils (approximately 0.04064 cm). With such sized tubes 24 , the openings 52 preferably have a diameter of about 0.154 inches (about 0.39116 cm) to provide an annular gap 53 with a cross-sectional area of about 0.0156 Sq.in (about 0.100645 cm ² ) , The size of the components, as shown, and generally as a function of the flow rates of the flows concerned, can vary significantly. The gaseous fuel generally makes up between about 10 to 40% of the total gaseous mixture of the fuel and the oxidant. About 25% of the mixture is preferably fuel.

In summary, there is an apparatus and method for mixing of fuel and an oxidizer for use in an automobile Thermal reformers provided the hydrogen to a fuel cell supplies. The device comprises a mixing container, a first inlet to the mixing tank for moving a gaseous fuel or Oxidant through this, a second inlet for moving one gaseous fuel or oxidant through this and one Outlet from the container adjacent to the autothermal reformer. The Discharge ends of the inlets are spaced apart from one another and from the outlet stands, which is provided in the vicinity of a POX reactor, the Mixture of fuel and oxidant that make up the mixing tank leaves, burns. The first inlet consists of a plate with a Variety of tubes extending therefrom and through which the Fuel or the oxidant is running. The tubes extend in the mixing container and towards the outlet of the container so that the fuel does not come into contact with the oxidizing agent, until the gaseous fuel or oxidizer from the ends of the pipes is discharged, which means the fuel with the Oxidati  agent in the gaseous state before being directed to the POX Reactor is mixed.

Claims (8)

1. Device for mixing gaseous fuel and an oxidizing agent for delivery to an autothermal reformer, comprising:
a mixing container for mixing the fuel and the gaseous oxidizing agent;
first and second inlets to the container for moving the fuel and oxidant therethrough, the first and second inlets having discharge ends spaced apart in the flow direction through the container; and
an outlet from the container spaced from the inlets and located adjacent a partial oxidation reactor (POX reactor) that burns the fuel and oxidant mixture exiting the mixing container;
the first inlet comprising a plurality of tubes, each having a discharge end through which the fuel or oxidant flows, and extending into the mixing container and toward the outlet so that the discharge ends of the tubes downstream of the discharge end of the second inlet are arranged to mix the fuel and the oxidizing agent sufficiently close to the POX reactor and thus preclude premature combustion of the mixture of fuel and oxidizing agent in the container. 2. Device according to claim 1, wherein the first inlet is configured to pass fuel to manage this. 3. Device according to claim 1, the second inlet being a plate with a plurality of openings gene includes, through which the tubes extend. 4. Container according to claim 3, the second inlet being configured to contain the oxidant to guide through this. 5. The device according to claim 1, the second inlet through a porous partition into the first and second chambers is divided. 6. The device according to claim 1, the second inlet being configured to pass steam therethrough to lead. 7. A method of delivering a mixture of fuel and air to an autothermal reformer that delivers hydrogen to a fuel cell, comprising the steps of:

• a) one of either fuel or air is fed into a mixing container at a first location;
• b) the other of fuel or air is introduced into the one fuel or air in the mixing vessel at a plurality of locations located downstream of the first location so as to form a substantially uniform mixture of fuel and air adjacent to the autothermal reformer , the plurality of sites being in a sufficient number to form the mixture in the immediate vicinity of the sites and being sufficiently distant from the first location so as to substantially preclude recirculation of the mixture upstream of the sites; and
• c) the mixture is discharged from the mixing container into the autothermal reformer;

wherein premature combustion of the mixture in the mixing container upstream of the autothermal reformer is averted. 8. A method of delivering a mixture of fuel and air to an autothermal reformer that delivers hydrogen to a fuel cell, comprising the steps of:

• a) mixing steam with one of either air or fuel to form a first substantially uniform mixture,
• b) the first mixture is fed into a mixing container at a first location;
• c) the other of fuel or air is introduced into the first mixture in the mixing vessel at a plurality of locations located downstream of the first location so as to form a second substantially uniform mixture of fuel, steam and air adjacent the autothermal reformer to form, the plurality of sites being present in a sufficient number to form the second mixture in the immediate vicinity of the sites and being sufficiently distant from the first site so as to recirculate the second mixture upstream of the sites essentially exclude; and
• d) the second mixture is discharged from the mixing container into the autothermal reformer;

wherein premature combustion of the second mixture in the mixing tank upstream of the autothermal reformer is averted.